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# Calcium Channel Blockers
## Overview
Calcium channel blockers (CCBs) are a class of drugs that reduce the influx of calcium ions into cardiac and vascular smooth muscle cells. This leads to vasodilation and/or decreased myocardial contractility and heart rate, depending on the specific agent. CCBs are divided into two main classes: dihydropyridines (DHPs) and non-dihydropyridines (non-DHPs).
## Primary Indications
* Hypertension
* Angina pectoris (stable, vasospastic)
* Supraventricular tachyarrhythmias (paroxysmal supraventricular tachycardia, atrial fibrillation/flutter rate control)
* Raynaud's phenomenon
## Adult Dosing
**Dihydropyridines (DHPs):** Primarily used for blood pressure and angina.
* Amlodipine: 2.5-10 mg orally once daily.
* Nifedipine (extended-release): 30-120 mg orally once daily.
* Felodipine: 5-10 mg orally once or twice daily, titrate up to 20 mg twice daily.
**Non-dihydropyridines (Non-DHPs):** Used for blood pressure, angina, and rate control.
* Verapamil:
* Hypertension: 80-120 mg orally two or three times daily. Max 480 mg/day.
* Angina: 80-120 mg orally two or three times daily. Max 480 mg/day.
* Rate control: 40-80 mg IV every 30-60 minutes for 4 doses, then every 1-4 hours as needed. Or 0.005 mg/kg/min IV infusion.
* Diltiazem:
* Hypertension: 30-60 mg orally two or three times daily, or extended-release 120-540 mg orally once or twice daily. Max oral daily dose varies by formulation.
* Angina: 30-60 mg orally two or three times daily. Max oral daily dose varies by formulation.
* Rate control: 0.25 mg/kg IV bolus, then 0.35 mg/kg IV infusion over 6 hours, then 0.2-0.5 mg/kg/hr infusion. Alternatively, 10-20 mg IV bolus, repeat after 15 mins if needed.
## Pediatric Dosing
Pediatric dosing is not well-established for many CCBs and should be guided by specialist recommendations and available literature. Dosing is often weight-based and may vary significantly by age.
* **Amlodipine:**
* Children 1-12 years: 0.05-0.3 mg/kg/day orally once daily. Max dose 5 mg/day.
* Adolescents 12-17 years: 2.5-5 mg orally once daily. Max dose 10 mg/day.
* **Verapamil:**
* Children < 1 year: Safety and efficacy not established. Use with caution if absolutely necessary.
* Children 1-15 years: 2-5 mg/kg/day orally divided into 3-4 doses. Max 10 mg/kg/day or 360 mg/day.
## Dose Adjustments
* **Hepatic impairment:** Doses may need to be reduced, especially for non-DHPs, due to increased bioavailability. Monitor closely for adverse effects.
* **Renal impairment:** Generally, dose adjustments are not required for CCBs unless severe renal impairment is present or specific drug formulations are used. Monitor renal function and electrolytes.
## Contraindications
* Severe hypotension
* Cardiogenic shock
* Certain heart blocks (e.g., second- or third-degree AV block without a pacemaker, sick sinus syndrome) unless a pacemaker is in place (non-DHPs)
* Symptomatic bradycardia (non-DHPs)
* Congestive heart failure with reduced ejection fraction (caution, especially with verapamil)
* Known hypersensitivity to the drug
## Adverse Effects
* **Common:** Peripheral edema, headache, dizziness, flushing, constipation (more common with verapamil).
* **Cardiovascular:** Hypotension, bradycardia (non-DHPs), reflex tachycardia (DHPs), AV block (non-DHPs), exacerbation of heart failure.
* **Gastrointestinal:** Nausea, vomiting, constipation.
* **Other:** Gingival hyperplasia (long-term use).
## Key Drug Interactions
* **CYP3A4 inhibitors/inducers:** Many CCBs are substrates of CYP3A4. Inhibitors (e.g., azole antifungals, macrolide antibiotics, grapefruit juice) can increase CCB levels, while inducers (e.g., rifampin, St. John's wort) can decrease levels.
* **Beta-blockers:** Additive effects on heart rate and contractility can lead to bradycardia, AV block, and heart failure.
* **Digoxin:** CCBs can increase digoxin levels. Monitor digoxin levels closely.
* **Statin:** Some statins (simvastatin, atorvastatin) are CYP3A4 substrates; concurrent use with CCBs can increase statin levels. Simvastatin maximum recommended dose is often limited when used with certain CCBs.
* **Aspirin:** May increase the risk of bleeding.
* **Cyclosporine/Tacrolimus:** CCBs can increase immunosuppressant levels. Monitor drug levels.
## Monitoring
* Blood pressure and heart rate for efficacy and adverse effects.
* Electrolytes (especially potassium).
* Renal and hepatic function.
* ECG for bradycardia or AV block (especially with non-DHPs).
* Signs and symptoms of heart failure.
* Signs of gingival hyperplasia.
## Clinical Pearls
* DHPs are generally preferred for hypertension and angina due to their potent vasodilatory effects and lower risk of cardiac depression.
* Non-DHPs (verapamil, diltiazem) are useful in rate control for atrial fibrillation and for patients with both hypertension and angina, but require careful monitoring for bradycardia and AV block.
* Start low and titrate slowly, especially in elderly patients or those with hepatic impairment.
* Constipation is a common dose-limiting side effect for verapamil.
* DHPs can cause reflex tachycardia, which may be undesirable in patients with angina. This can often be mitigated by co-administration with a beta-blocker.
* Extended-release formulations improve adherence and reduce peak-trough fluctuations, leading to fewer side effects.
**Disclaimer:** This information is intended for healthcare professionals as a quick reference. Always consult the most current prescribing information approved by the FDA and consider individual patient factors and local guidelines before making any clinical decisions.
